The present invention relates in general to combination locks, and more particularly to combination locks of the tumbler wheel type having a wheel tension adjuster mechanism permitting the tension on the stack of tumbler wheels to be set properly to achieve a predetermined torque in operation of the lock.
Conventional locks of the class known as combination locks usually comprise three or four tumbler wheels which are loosely journaled in a coaxial, side-by-side spaced stack for rotation within a lock casing on a tubular arbor or tumbler post projecting inwardly from the front wall of the casing or from the rear cover plate. The lock dial, which usually has 100 peripheral calibration marks thereon, is affixed to a dial spindle which extends through the bore of the tumbler post and has keyed to the inner end thereof a disc-like drive cam which is likewise arranged coaxially with and spaced rearwardly from the stack of tumbler wheels. A drive pin projects forwardly from the drive cam and with a conventional fly rotatable through a limited arc and associated with the rearmost tumbler wheel, provides a lost motion coupling to drive the tumbler wheel in selected relation to the drive cam. A similar lost motion coupling is provided between each of the successive tumbler wheels so that each of the tumbler wheels may be driven upon predetermined rotation of the drive cam. A thin spacer washer is also customarily provided between each of the tumbler wheels. Each of the flies or fly members between the successive tumbler wheels and between the rearmost tumbler wheel and the drive cam typically comprise a ring portion journaled in concentric relation with the associated tumbler wheel and a radial projection which lies between a pair of stop shoulders disposed to abut portions of the radial projection and limit angular rotation of the fly to about 20.degree. or other desired limited angular range. A drive pin or lug projects from the adjacent tumbler wheel into position to abut the radial projection of the fly and transmit rotation to the adjacent tumbler wheel after the fly has moved through its predetermined lost motion angular range. Each of the tumbler wheels and the drive cam is provided with a peripheral notch or gate at a selected radial position on the drive cam and tumblers.
A fence lever which is pivotally connected near one end on a reciprocative bolt member slidably supported in the lock casing is provided with a depending nose near the opposite or free end of the fence lever which is designed to ride upon the drive cam periphery, in conventional combination locks, and has a bar or fence projecting laterally from the fence lever in overlying relation to the peripheries of the tumbler wheels. The position of the fence in relation to the length of the fence lever nose is usually such that the fence is spaced slightly outwardly from the peripheries of the tumbler wheels when the fence lever nose is riding on the drive cam periphery.
The combination lock is opened, in the case of such conventional combination lock structures, by rotation of the dial in a predetermined sequence in clockwise and counterclockwise directions through predetermined numbers of revolutions to a series of numerical positions indicated by alignment of numbers or indicia on the lock dial with a fixed index adjacent the lock dial periphery, to dial a predetermined series of combination numbers and thereby effect angular rotation of the plurality of tumbler wheels to positions which result in alignment of the tumbler wheel peripheral gates with the fence, and the dial is then rotated to bring the drive cam gate to a position registered with the fence lever nose to cause the fence lever nose and fence to drop into the gates whereupon further rotation of the dial through a partial revolution in a predetermined direction achieves retraction of the bolt.
Also, combination locks have been provided with various types of guard or shielding mechanisms mounted on the drive cam to resist detection of the "feel" of the points of engagement of the fence lever nose with the driving cam gate in accordance with well-known lock manipulation procedures to resist opening of the lock by unathorized persons who do not have authorized knowledge of the combination to which the lock has been set. Examples of such locks designed to defeat unathorized detection of the lock combination are found in prior U.S. Pat. Nos. 2,575,674 and 2,807,954 as typical examples.
For various reasons, it has been found desirable to provide such combination locks, either of the conventional type or of the detection resistant type, with means for applying variable tension forces to the stack of tumbler wheels to effect adjustment at the factory or in the field, of the torque characteristics of the tumbler wheels and operating mechanism therefor, so that the lock can be set to different torque values or specification requirements and will maintain a constant torque at the desired setting throughout the useful life of the lock, or be capable of readjustment to maintain the predetermined desired torque characteristics. For example, the United States Government typically specifies that a fifteen ounce torque level be provided on the tumbler wheels of combination locks when delivered, providing a margin of safety above the torque level actually needed to protect the lock against vibration of the tumbler wheels to positions making compromise of the lock by unauthorized persons easier. While prior combination locks of the tumbler wheel type have been provided, in some patent disclosures, with a bowed or curved spring washer or disc, either between successive tumbler wheels or between the forwardmost tumbler wheel and the stack of tumbler wheels and the front wall of the lock casing, we are aware of no prior tumbler wheel combination locks having a means for setting the torque characteristics of the tumbler wheel stack and the rotatable operating components of the lock to different tensions or torque settings and wherein the tension forces on the stack of tumbler wheels and the torque properties thereof can be changed to different tensions or torques by an adjuster wrench or tool during manufacturer assembly of the lock or in the field.
An object of the present invention, therefore, is the provision of a novel combination lock construction of the tumbler wheel type, wherein means are provided for setting and varying the wheel tension force or torque characteristics of the lock.
Another object of the present invention is the provision of a novel combination lock having a stack of tumbler wheels and a rotatable dial and drive cam assembly for adjusting the same, wherein a torque adjustment mechanism is incorporated in the lock adjustable by a tool or wrench introduced into the lock mechanism chamber for setting the wheel tension or torque characteristics to a desired value and for adjusting or changing the tension or torque characteristics of the stack of tumbler wheels.
A further object of the present invention is the provision of a combination lock having a plurality of tumbler wheels arranged in a stack associated with a driving cam and a rotatable dial for operating the same, having a ramp mechanism and angularly adjustable tension applying spring member movable on the ramp mechanism to different angular positions applying different spring tension forces to the stack of tumblers for adjusting the torque thereof, together with means responsive to insertion and operation of a tool into the lock mechanism chamber to effect angular adjustment of the tension force applying spring means.
Other objects, advantages and capabilities of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings illustrating preferred embodiments of the invention.